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1. Field of the Invention
The invention relates in general to distributed monitoring of remote sensors, and in particular to novel systems which are useful for remote monitoring of chemical properties or electric current.
2. Related Art
Over the last three decades the United States has spent billions of dollars trying to monitor and clean up contaminated ground water and soils as a result of a period in which the industrial expansion of our Nation outpaced our knowledge of safe chemical disposal. Despite large sums of financial investment to protect and recover natural resources, scientists continue to struggle to accurately monitor ground water and detect contaminants, or quantify the effect of contaminants on the ecosystem as a whole. This struggle is due to two primary reasons: 1) there is a lack of advanced, field deployable, environmental sensory systems capable of continuous, long-term monitoring of physical, chemical, and biological measurands, and 2) there are major problems associated with biofouling of the sensors due to nutrient overloading and algae growth.
The presence of chemicals and complex molecules determines the health of a water source in relation to the ecosystem as a whole, and is typically classified into two groups: primary and secondary contaminants. The former group, which includes heavy metals, radionucliotides, and dioxins, is often characterized as those contaminants that are stable in nature and resist breakdown due to sunlight or temperature, or do not dissolve easily into a water system. These primary contaminants often lead to localized hot spots within an ecosystem, resulting in complete devastation of the normal localized aquatic balance in addition to becoming a point source for continuous contamination for decades to come. By contrast, the latter group is known as the effect group, and is characterized by the overall change in traditional water quality monitoring parameters which include dissolved oxygen (DO), pH, dissolved solids, nitrate-nitrite nitrogen (NNN), and total phosphorous (TP).
Historically, monitoring of contaminants or their effects has been done through discrete sampling of contaminated sites at random intervals. The samples are then processed off-line through wet-chemistry methods, often several days or weeks after the sample was gathered. The most significant impact of this methodology is that notification of events affecting the change in water quality parameters do not occur until after the change has caused some form of catastrophic event, such as illness or death in humans or an entire stretch of river dying due to total consumption of dissolved oxygen. Additionally, discrete random sampling also causes uncertainty; with no temporal correlation of the data, it is often difficult to determine what was a cause and what was an effect.
Sensor technology for measuring contaminants or their effects on the ecosystem continues to improve. Optical-based sensors are especially promising due to their inherent advantages with respect to sensitivity, large dynamic range, immunity to electromagnetic interference, and lightweight profiles. For example, optical techniques demonstrating heavy metals detection and classification have been published as have techniques for detecting biological agents, H2S, and the aforementioned water quality parameters NNN, CO2, DO, and pH.
Unfortunately, sensor technology for detection is not the total solution. Real-world problems such as biofouling, environmental extremes, and issues involving data, such as transport mechanisms, storage, and analysis, need to be addressed in parallel with improvements in sensor technology to affect significant advances in monitoring the world""s natural resources.
As with the field of environmental monitoring discussed above, monitoring technologies in the field of electrical power generation, distribution, and transmission have also been subjected to technical limitations and inefficiencies. Having timely knowledge of past and present static and dynamic states in power generation facilities and distribution and transmission grids is critical in decision making, power scheduling, billing, model studies, planning protection, and maintenance. To date, the task of collecting data on a distributed power system has been relegated to a collection of disassociated electronic subsystems scattered throughout the grid. All are ordinarily standalone designs, most having no high-throughput networking provisions and, at best, only the most recent designs employ any digital capability (mass storage, rule-based triggering, adaptive process tailoring, etc.). Most previously installed measurement systems were designed specifically for a particular task and the concept of integrating all measurement components into a single body was not possible for a host of varied reasons. It is not uncommon to find decision-makers located in the control room at a major utility with three or more computer terminals on their desks with virtually no way to pass information between them.
Within the last few years, the most important pressure upon electric-power utilities has been the result of deregulation and the subsequent economic competition that it has promoted. In order to remain competitive and profitable, providers of electric power have been forced to review all aspects of their operations and seek methods that improve efficiency. Of the numerous areas identified where cost savings could be implemented, improving power transfer efficiency, real-time control of power networks, and detection and prevention of potential line fault conditions through online monitoring all rank in the top target areas for focus and development.
A major impediment to improved power transfer efficiency is existing transducer technology. Virtually unchanged over the last several decades, conventional current/potential transformers are characterized by their bulkiness, expense, geometry, large volumes of electrical insulation required when used on high-voltage lines, and potential for catastrophic failure. With respect to real-time control of power networks and the detection/prevention of line fault conditions, most types of conventional transformers exhibit significant bandwidth limitations, restricting their usefulness in the monitoring of harmonics and subsequent determination of power quality or the exact timing of line fault events.
A 1995 article by the Electrical Power Research Institute (EPRI) indicates that a 1% increase in efficiency due to improved sensors and instrumentation in coal-fired generator plants translates to a savings of over $300 million per year. Moreover, a 1% increase in capacity utilization throughout the utilities due to advanced instrumentation would result in over $3 billion in saving per year for the industry.
On Jul. 2, 1996, a short-circuit on a 345-kV line in Wyoming started a chain of events leading to the breakup and complete islanding of the western North American power system. Loads were very high due to local demand in southern Idaho and Utah because of temperatures around 100xc2x0 F. Simultaneously, power exports from this region to California were high, causing many of the distribution lines to operate near capacity. A flashover to a tree at 2:24 p.m. initiated a chain of events, and when coupled with the failure of equipment and harmonic instability within the power distribution network, numerous protective devices kicked in to isolate a 5-state area. The impact was a total loss of power for over 15 million commercial and residential customers and a total estimated revenue loss approaching $2,000,000,000. Furthermore, post analysis of the data that does exist from this outage has indicated that if a real-time, bi-directional communications system had been in place, operators or computers would have had approximately 110 seconds to prevent collapse of the entire grid system, potentially saving the utilities and their customers hundreds of millions of dollars.
It is therefore an object of the invention to provide an improved system and method for remote monitoring.
It is a further object of the invention to provide a remote monitoring system and method which provides the capability of delivering sensor data to monitoring facilities in a timely manner, whereby catastrophic environmental or power delivery events can be forseen and averted or minimized.
It is a further object of the invention to provide a remote monitoring system and method which can be practiced in a less costly and less labor-intensive manner than those of the prior art.
In a preferred embodiment, the invention provides a system for gathering, transmitting, and storing data captured from remote monitoring sites positioned in the field, with specific applicability to distributed chemical sensing and reporting, as well as distributed power monitoring and reporting. Transducers monitoring water quality parameters or electrical power parameters have their data transmitted to the Internet or Intranet via a communications link. From here, the data is relayed to secure servers where it is formatted, analyzed, and stored for later retrieval by a customer. If alarm conditions exist that require immediate customer notification, notifications are sent via one or more telecommunications means, including pager, cellular telephone, or email. With respect to the distributed chemical sensing embodiments, the invention preferably utilizes fiber optic chemical sensors that addresses the problem of biofouling. Using anti-fouling measures, the invention can provide continuous, long-term waterway monitoring. With respect to distributed power monitoring and reporting, the invention preferably utilizes a fiber optic optical current transducer system for the measurement of magnetic fields in electric power and power electronic applications. The transducer is based upon rare-earth iron garnet (REIG) crystals that exhibit the Faraday effect when placed in a magnetic field. This transducer is extremely lightweight, making retrofitting of existing distributed power monitoring grids extremely cost effective. In both cases, the respective sensor technologies are coupled with wireless telecommunications and network infrastructures to provide businesses with the ability to shift from a reactive to a proactive mode of operation, enabling them to become more efficient in their business operations.